CloudMigrations: Add warnings for bugs with HA setups (#107265)

add warnings for HA bug

docs/sources/administration/migration-guide/cloud-migration-assistant.md

@@ -49,6 +49,7 @@ To use the Grafana migration assistant, you need:
 - [`Admin`](https://grafana.com/docs/grafana-cloud/account-management/authentication-and-permissions/cloud-roles/) access to the Grafana Cloud Stack. To check your access level, go to `https://grafana.com/orgs/<YOUR-ORG-NAME>/members`.
 - [Grafana server administrator](https://grafana.com/docs/grafana/<GRAFANA_VERSION>/administration/roles-and-permissions/#grafana-server-administrators) access to your existing Grafana OSS/Enterprise instance. To check your access level, go to `https://<GRAFANA-ONPREM-URL>/admin/users`.
 - Internet access from your existing Grafana OSS/Enterprise instance.
+- If you are running Grafana in a [highly-available setup](https://grafana.com/docs/grafana/latest/setup-grafana/set-up-for-high-availability/), we recommend scaling Grafana down to one replica to avoid a [known bug](https://github.com/grafana/grafana/issues/107264).
 - If your network requires external services to be on an allowlist to allow access, add the following IPs and URLs to your allowlist:
   - [Hosted Grafana](https://grafana.com/docs/grafana-cloud/security-and-account-management/allow-list/#hosted-grafana)
   - [Hosted Alerts](https://grafana.com/docs/grafana-cloud/security-and-account-management/allow-list/#hosted-alerts)

pkg/services/cloudmigration/cloudmigrationimpl/snapshot_mgmt.go

@@ -659,7 +659,8 @@ func (s *Service) uploadSnapshot(ctx context.Context, session *cloudmigration.Cl
 	// nolint:gosec
 	indexFile, err := os.Open(indexFilePath)
 	if err != nil {
-		return fmt.Errorf("opening index files: %w", err)
+		// TODO: Clean this notice once we've fixed the HA bug
+		return fmt.Errorf("opening index files: %w. If you are running Grafana in a highly-available setup, try scaling down to one replica to avoid a known bug: https://github.com/grafana/grafana/issues/107264", err)
 	}
 	defer func() {
 		if closeErr := indexFile.Close(); closeErr != nil {